Strategy for using the envelope information within a closed loop power control system

ABSTRACT

A power control system includes a reference path filter used to suppress high frequencies in an input signal and generate a filtered envelope signal, a reference path amplifier to scale the filtered input signal based on a gain signal and generate a reference signal, a signal path amplifier to amplify an RF modulated signal and generate a signal path output signal scaled by a gain of an actuator signal, and a power detector to detect a power associated with the signal path output signal. The system includes an ADC to receive, pre-filter and convert the detected envelope signal into a measurement signal, and a comparator block to receive the reference signal and the measurement signal, and generate an error signal based on the difference, and a controller to generate the actuator signal for controlling the gain of the signal path amplifier based on the error signal.

BACKGROUND

In the UMTS system, the power of a mobile station (MS) telephone must betightly controlled so that this level is neither too low nor too high.For example, in a CDMA access system, excess output power of a MS mayimpede other connections on the same channel.

During a connection, the base station (BS) regularly sends (at a rate of1.5 kHz) commands to the MS which give a correction to the output power.These commands are defined in 3GPP 25.101 and they are generallycommunicated at between −3 and +3 dB. The MS is required to effectivelyand consistently respond with an increase in output power when commandedto output a higher level and vice versa, otherwise the entire channeland all the connections could suffer. Further, step tolerances arespecified and the total dynamic range is required to be more than 70 dB.

In the past an open loop concept has generally been used in UMTStelephones; that is, the power was not directly monitored within thetelephone hardware.

However, new requirements on tolerances and on effective radiated outputpower require phone manufacturers to switch to a closed loop approach,in particular, to optimize performance when the antenna is mismatched,while guaranteeing that the specified maximum radiation (SAR) is notovercome. Closed loop systems have long been used in GMSK systems(constant envelope), but their use for UMTS systems is made much moredifficult by the presence of wide bandwidth amplitude modulation havinga large crest factor as well as requiring that the power stabilizewithin 50 us.

Accordingly, there is a continued need to improve closed loop powercontrol in UMTS systems.

SUMMARY

The following presents a simplified summary in order to provide a basicunderstanding of one or more aspects of the disclosure. This summary isnot an extensive overview, and is neither intended to identify key orcritical elements of the disclosure, nor to delineate the scope thereof.Rather, the primary purpose of the summary is to present some conceptsin a simplified form as a prelude to the more detailed description thatis presented later.

In one embodiment, a closed loop power control system is disclosed thatincludes a reference path filter coupled to an input signal, configuredto suppress high frequencies in the input signal and to generate afiltered envelope signal. The system also includes a reference pathprogrammable gain amplifier (PGA) coupled to the reference filter and again signal, configured to scale the filtered envelope signal based onthe gain signal and generate a reference signal therefrom, and a signalpath PGA, configured to receive and amplify an RF modulated signal, andgenerate a signal path output signal scaled by a gain of an actuatorsignal. The system has a power detector, configured to detect a powerassociated with the scaled signal path output signal and to generate adetected envelope signal therefrom, and an analog to digital converter(ADC) coupled to the power detector configured to receive, pre-filterand convert the detected envelope signal into a measurement signal. Thesystem also has a comparator block configured to receive the referencesignal from the reference path amplifier and the measurement signal fromthe ADC, and generate an error signal based on the difference betweenthe reference signal and the measurement signal, and a controllercoupled between the signal path amplifier and the comparator block,configured to receive the error signal from the comparator block andgenerate the actuator signal operable to control the gain of the signalpath amplifier based on the error signal.

In one embodiment, a method is disclosed for closed loop power controlusing the slow varying envelope information of an input signal. Themethod comprises suppressing high frequencies in the input signal togenerate a filtered UMTS envelope signal, and amplifying the filteredUMTS envelope signal with a closed loop gain to generate a referencesignal therefrom. The method also comprises amplifying an RF modulatedsignal to generate an amplified output signal scaled by a gain of anactuator signal, and detecting a power associated with the amplified andRF modulated signal to generate a detected envelope signal therefrom.Finally, the method further includes converting the detected envelopesignal into a measurement signal, generating an error signal based on adifference between the reference signal and the measurement signal, andgenerating the actuator signal for controlling the gain of the amplifiedoutput signal based on the error signal.

The following description and annexed drawings set forth in detailcertain illustrative aspects and implementations. These are indicativeof only a few of the various ways in which the principles may beemployed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified schematic diagram of a closed loop power controlsystem in accordance with one embodiment of the disclosure;

FIG. 2 is a simplified schematic diagram of a closed loop power controlsystem utilizing envelope information for output power control, inaccordance with one embodiment of the disclosure;

FIG. 3 is a simplified schematic diagram of a closed loop power controlsystem utilizing envelope information for power control of the system,in accordance with one embodiment;

FIG. 4 is a simplified comparator block such as may be used in theclosed loop power control system of FIG. 3, in accordance with oneembodiment;

FIG. 5 is a simplified block diagram of one embodiment of a controllersuch as may be used in the closed loop power control system of FIG. 3,in accordance with one embodiment of the disclosure;

FIG. 6 is a simplified block diagram to explain the performance of alogarithmic comparator block as shown in FIG. 4.

DETAILED DESCRIPTION

One or more implementations will now be described with reference to theattached drawings, wherein like reference numerals are used to refer tolike elements throughout. Systems and methods are disclosed forefficiently amplifying and adjusting the output power of a closed looppower control system employing the slow varying envelope information inthe input signal for the power control loop.

Because a UMTS transmitter must maintain accurate absolute power controlover the transmission signal (especially on the maximum output power and20 dB below), there is a continued need to improve power control in UMTSRF power amplifier systems that operate in the GHz spectrum. This levelof absolute power control can likely only be met with a closed looppower control system.

Accordingly, a closed loop power control method for RF power amplifiersis provided in one embodiment for closed loop power control of an inputsignal such as a UMTS input signal based on using the slow varyingenvelope information. The power control system is suitable for base andmobile stations and other applications that could use such closed loopcontrol of RF power amplifiers.

Turning now to FIG. 1, a simplified schematic diagram of a closed looppower control system is illustrated in accordance with one embodiment.In one embodiment, the power control system 100 comprises an inputsignal 102 (e.g., a UMTS, CDMA, WDCMA, GSM, 3GSM, baseband or digitalamplitude information input signal) which is up-converted into amodulated RF signal 108 with an RF local oscillator signal 106 utilizingmixer 110. The modulated RF signal 108 is then amplified using aprogrammable gain amplifier (PGA) 112 whose gain is controlled by acontrol signal 115 to provide an amplified RF modulated signal 114. Theamplified RF modulated signal 114 is then power amplified by poweramplifier (PA) 116 which generates a RF transmission signal 118, forexample, which is delivered to an antenna 119.

The power control system 100 also has a power detector 122 thatdemodulates the RF transmission signal 118 into a detected power signal124 proportional to the envelope of the RF transmission signal 118. Thepower control system 100 further includes an analog to digital converter(ADC) 128 coupled to the power detector 122 that pre-filters (e.g.,containing an anti-aliasing low pass filter), samples and converts thedetected power signal 124 into a measurement signal 130. The powercontrol system 100 also includes a comparator 132 that receives adesired closed loop gain used as a reference signal 104 and themeasurement signal 130 from the ADC 128, and generates an error signal134 based on the difference between the reference signal 104 and themeasurement signal 130. Finally, the power control system 100 also has acontroller coupled between the PGA 112 and the comparator 132,configured to receive the error signal 134 from the comparator 132 andgenerate the control signal 115 for control of the gain of the PGA 112.

As long as an error between the reference signal 104 and the measurementsignal 130 exists, the control signal 115 is adjusted. However, in thepower control solution 100 of FIG. 1, the frequency contents below theloop bandwidth are removed from the RF transmission signal 118 deliveredto the antenna 119 due to the closed loop operation. For some UMTSconstellation signals this may have a large impact on the quality of themodulated UMTS signal at the antenna, for example, poor quality ofoutput at the antenna, and poor spectral performance. Effects due totemperature or component variations are well compensated due to theclosed loop system. Thus, with the topology of FIG. 1, it is difficultto compensate the information lost in the slow varying frequencycontent.

FIG. 2 illustrates a closed loop power control system 200, utilizingenvelope information for control of the output power of the system, inaccordance with one embodiment of the disclosure.

While the power control system 200 will be described herein with one ormore identified programmable gain amplifiers PGAs, a power amplifier(PA), complex up-converters or mixers, complex filters, a low-passfilters (LPF), a comparator, a detector, an analog to digital converter(ADC), and a digital-to-analog converter (DAC), as one example, itshould be understood that many variations of such components andfeatures can be made, and all such variations are contemplated asfalling within the scope of the disclosure. Closed loop power gaincontrol can also be carried out by other means also contemplated withinthe scope of the disclosure.

In one embodiment, the power control system 200 comprises an inputsignal 202 (e.g., a UMTS, CDMA, WDCMA, GSM, 3GSM, baseband or digitalamplitude information signal) that enters a signal path 203, where inputsignal 202 is up-converted into a modulated RF signal 208 by an RF localoscillator signal 206 utilizing a signal path mixer or up-converter 210.The RF modulated signal 208 is then amplified by signal path amplifier212, for example, using a programmable gain amplifier (PGA) whose gainis programmably controlled or scaled by an actuator signal 215 toprovide an amplified RF modulated output signal or scaled signal pathoutput signal 214. The scaled signal path output signal 214 is thenpower amplified by power amplifier (PA) 216 to generate an RFtransmission signal 218, for example, which is delivered to an antenna219 (not shown). The antenna 219 coupled to the power amplifier 216, canthen be used, for example, to transmit the RF transmission signal 218.

The power control system 200 also has a power detector 222 that detectsa power level 224 associated with the RF transmission signal 218, forexample, by detecting and demodulating an envelope signal of the RFtransmission signal 218. The power control system 200 further includesan analog to digital converter (ADC) 228 coupled to the power detector222. The ADC 228 pre-filters (e.g., using an anti-aliasing low passfilter), samples and converts the detected envelope signal 224 into ameasurement signal 230 (e.g., a digital measurement signal 230).

The power control system 200 also has a reference path filter 250coupled to the input signal 202, configured to suppress high frequenciesin the input signal 202 (e.g., using a low-pass filter) and generate afiltered envelope signal 252. The power control system 200 furtherincludes a reference path amplifier 254 coupled to the reference filter250 and a (closed loop) gain signal 204 that is configured to scale thefiltered envelope signal 252 to the gain signal 204 and generate areference signal 205 therefrom.

The power control system 200 also includes a comparator 232 thatreceives the reference signal 205 and subtracts the measurement signal230 to generate an error signal 234 based on the difference between thereference signal 205 and the measurement signal 230. Finally, the powercontrol system 200 also has a controller 240 coupled between the signalpath amplifier 212 and the comparator 232, configured to receive theerror signal 234 from the comparator 232 and generate the actuatorsignal 215 for feedback control of signal path amplifier 212 by scalingthe gain of the signal path amplifier 212. The controller may further beconfigured to integrate and/or low-pass filter the error signal 234 inthe generation of the actuator signal 215.

Although one signal path amplifier 212 is illustrated and describedherein, two or more programmable gain amplifiers and/or switched modeamplifiers and/or switched mode power amplifiers (SPA) may be utilizedin the PGA or signal path amplifier 212 or in power amplifier PA 216.Further, the power amplifier 216 may be combined with or integrated intothe signal path amplifier 212 as one or more extra power gain stages ofthe amplifier, and all such variations and combinations are contemplatedherein.

Thus, the power control system 200 is configured to scale the inputsignal 202 by the actuator signal 215 based on a mismatch between thereference signal 205 generated on a reference signal path 250 and themeasurement signal 230 generated on a feedback path 260. In oneembodiment, such mismatches would be based on variations in the detectedenvelope signal 224. Accordingly, the power control system 200 isresponsive to low frequencies in the feedback path 260 and may thus beused to monitor a slowly varying amount of envelope information forclosed loop power control of the system. For example, such slowlyvarying envelope information detected in the feedback path 260 is alsoincluded in the measurement signal 230. So the error signal 234 is nowfree of slowly varying envelope information and only responds to theinfluence of component and temperature variations. In comparison to FIG.1, the slow varying envelope information is now not removed from the RFtransmission signal 218 and improves the quality of the signal comparedto the method described in FIG. 1.

By contrast to the power control system 100 of FIG. 1, the power controlsystem 200 of FIG. 2, achieves a better bandwidth matching between thereference signal path 250 and the feedback path 260. For example, in thepower control system 100 of FIG. 1, the closed loop gain signal on thereference signal 104 would generally have a constant value compared tothe varying measurement signal 130 of the feedback path, therebyproducing a large bandwidth mismatch between these signals when comparedby comparator 132. By contrast, in the power control system 200 of FIG.2, the reference signal 205 in the reference path 250 has a dynamicquality provided by the input signal 202 and the reference path filter250, which more closely matches the bandwidth characteristics of themeasurement signal 230 provided by the feedback path 260. Accordingly,comparator 232 of FIG. 2 is able to more easily compare and respond tosubtle power variations in the output power of the transmission signal218, for example.

FIG. 3 illustrates a closed loop power control system 300, utilizingenvelope information for power control, in accordance with anotherembodiment. Power control system 300, for example, comprises a signalpath 301, a reference path 350 and a feedback path 360, each comprisingrespective components illustrated and discussed in the following. In thesignal path 301 of the power control system 300, the amplitude componentA(iT) 302 is amplified by first, second and third signal path PGAs 312a, 312 b and 312 c, respectively, converted by DAC 313 to an analogsignal, and upconverted by a carrier signal 306 using a signal pathmixer 310. Power control system 300 may also comprise in the signal path301, a power amplifier 316 which receives a scaled PGA output signal 314from the third signal path PGA 312 c and generates a transmission signal318 that may be delivered to an antenna (not shown).

In the reference path 350, power control system 300 also comprises adelay adjustment block 352 coupled to the input signal 302 (e.g., aUMTS, CDMA, WDCMA, GSM, 3GSM, baseband or digital amplitude informationsignal) to adjustably delay the input signal 302, and a reference pathPGA 354 configured to amplify the output of the delay adjustment block352, which is scaled according to a gain associated with a controllersignal 342 supplied to the reference path PGA 354. The reference path350 of the power control system 300 also includes a digital filtercoupled to the scaled reference PGA output signal of the reference pathPGA 354, configured to suppress high frequencies in the scaled referencepath PGA output signal and to generate a reference signal 305.

The feedback path 360 of power control system 300 comprises a powerdetector 322 operably coupled to the third signal path PGA 312 c,configured to detect a power associated with the scaled PGA outputsignal 314 (or the transmission signal 318) and generate a detectedenvelope signal 324 therefrom, an analog low pass filter 328 coupled tothe power detector 322 to selectively filter high frequencies from thedetected envelope signal 324, an analog offset compensation circuit 364and a feedback path mixer 362 which are configured to provide offsetcompensation as needed, an analog to digital converter (ADC) 370configured to receive, pre-filter and convert the detected envelopesignal 324 into a filtered digital measurement signal, and a digitalfilter 380 coupled to the ADC 370, configured to suppress highfrequencies in the digital measurement signal and to generate ameasurement signal 330.

The feedback path 360 of power control system 300 may further comprise afeedback path PGA 368 to provide additional signal gain to the detectedenvelope signal 324, an offset compensation circuit 372 and 374, and again compensation circuit 376 and 378 configured to generate offset andgain compensation, respectively, for the digital measurement signal fromthe ADC 370.

The power control system 300 further comprises a control circuit 348which includes a comparator block 332 configured to receive thereference signal 305 from the reference path 350 and the measurementsignal 330 from the feedback path 360, and generate an error signal 334based on the difference between the reference signal 305 and themeasurement signal 330. The control circuit 348 of the power controlsystem 300 also includes a controller 340 coupled between a gaindistribution unit 345 and the comparator block 332 configured to receivethe error signal 334 from the comparator block 332 and a wanted gaininput signal 341 and generate the control signal 315 operable to controlthe gain of the gain distribution unit 345. The wanted gain input signal341 is also operable to control the gain of the reference path PGA 354.The control circuit 348 of the power control system 300 also comprisesthe gain distribution unit 345 coupled between the controller 340 andthe first, second and third signal path PGAs 312 a, 312 b and 312 c,respectively, the gain distribution unit 345 configured to receive thecontrol signal 315 from the controller 340 and generate the actuatorsignal(s) 315 a-315 f operable to control the gain of the first, secondand third signal path PGAs 312 a, 312 b and 312 c, respectively, basedon the error signal 334.

Thus, in accordance with one aspect of the disclosure, the power controlsystem 300 of FIG. 3 thereby provides a digital control loop thatutilizes amplitude information from the baseband signal input 302, and acomparator 332 that essentially uses the ratio of the reference signal305 and the measurement signal 330 and not just the difference of thesesignals. In another aspect of the power control system 300 of FIG. 3,the controller 340 compensates the gain within the signal path 301 aswell as the gain within the reference path 350. In yet another aspect,the gain step response on the reference path 350 and on the signal path301 plus the feedback path 360 are matched.

In operation, the digital amplitude information A(iT) 302 is convertedto an analogue signal which goes through a chain of buffers, mixers(e.g., one or more mixers, depending on the transmit architecture) andRF amplifiers (e.g., PGAs 312 a, 312 b and 312 c) until it reaches thepower amplifier PA 316. The power detector 322 generates an analoguesignal whose amplitude is proportional to the power of the forwardtraveling RF wave. One embodiment of a power detector 322 may comprisean RF coupler having a high directivity and a peak detector. Thisdetected envelope signal 324 contains at least part of the originalamplitude modulation information A(iT) 302 and can be advantageously lowpass filtered, for example, by filter 328 in order to limit thebandwidth of the signal, the timing requirements between the referencepath 350 and the feedback path 360 in relation to the amplitudemodulation (which is different from timing requirements on the appliedgain steps), and the requirements on the envelope accuracy of the powerdetector 322 (e.g., zero crossings due to modulation distort theenvelope signal, if amplified with a limited bandwidth).

The resulting detected envelope signal is then sampled by an ADC 370,digitally compensated for a remaining offset and a gain error (e.g.,using gain compensation circuit 376/378 and offset compensation circuit372/374), which may be introduced by the power detector 322, but mayalso be due to the ADC 370 or the analogue low pass filter 328. If theADC 370 and the analogue low pass work ideally, the gain and offsetcompensation could be summarized to an inverse power detector. Toachieve a perfect matching between the reference path and the feedbackpath (mainly due to process tolerances of the analogue low pass filter328) the signal is filtered with a digital filter 380 before it entersthe comparator block 332. The digital filter stage 380 can also be usedto increase the quantization within the feedback path 360. Due to thelinearity of the feedback path 360 the order of the blocks may berearranged, as it may only change the linearity requirements for theblocks.

The reference path 350 has two inputs: the digital amplitude input A(iT)302 and the gain provided by the controller signal 342 delivered fromthe controller 340. Conventional systems would typically apply thewanted gain 341 directly to the reference path 350, but in the closedloop power control system 300 concept due to the settling timerequirement of the entire system, the gain on the reference path 350 isadditionally modified by the controller 340. The digital amplitude isfirst delay adjusted using delay adjustment 352, amplified by referencepath PGA 354 to the expected output signal and then processed with adigital filter 356 whose step response is similar to the cascade of thefilters present in the feedback path 360. In the feedback path 360, theorder of the circuit blocks aids in the reduction of the settling timeof the whole system, as described further below.

Ideally, the output signals (e.g., 305 and 330) on the reference path350 and feedback path 360, respectively, seek to achieve nearlyidentical bandwidth characteristics. However, in real world this goal isnot so easily achieved, and that is why the power control system 300 ofFIG. 3 is needed.

The comparator block 332 compares the reference signal 305 to themeasurement signal 330, and generates the error signal 334 according tothe following explanation. The gain of a simple amplifier for example isdefined as ratio of the output signal compared to the input signal. Thisidea behind this principle suggests one possible implementation for thecomparator block 332 as represented in FIG. 4.

For example, FIG. 4 illustrates a simplified comparator block 332 suchas may be used in the closed loop power control system 300 of FIG. 3, inone embodiment.

In another embodiment, the ratio could be calculated directly withoutthe use of a logarithm of the reference signal 305 from the referencepath 350 and the measurement signal 330 from the feedback path 360. Theerror signal 334 from the comparator block 332 is now essentially thegain error between the reference path 350 and the feedback path 360. Theadvantage of this topology is that the error signal 334 at the output ofthe comparator block 332 is only a function of the gain error betweenthe two different paths and not dependent on the reference or feedbackamplitude as compared to traditional control concepts. The error signal334 may then be fed directly into the controller 340.

The controller 340 is configured to combine the wanted gain 341 and theerror signal 334 from the comparator block 332.

FIG. 5, for example, illustrates a simplified block diagram of oneembodiment of a controller 340, such as may be used in the closed looppower control system 300 of FIG. 3.

FIG. 6 illustrates the behavior 600 on the error signal when thecomparison block contains logarithmic blocks. If a wanted gain isapplied at time equal to zero, the AM-signal 302 will be immediatelyamplified as expected. In the signal path 301/feedback path 360 thepresence of an additional physical gain error (e.g., 334) scales theAM-signal 302 differently than the reference path 350. After low passfiltering and logarithm on each path, the error signal 334 willgenerally correspond to the physical gain error (e.g., −6 dB).

Advantageously, in the power control systems 200 of FIG. 2 and 300 ofFIG. 3, the error signal is available even during the settling of thefilters on each path (reference path 350 and signal path 301/feedbackpath 360, or reference path 350. If needed, the controller 300 responserate may be increased, only limited by the accuracy of the digitalimplementation and the matching between the reference path 350 and thefeedback path 360. Accordingly, the controller 340 generally seeks totime synchronize the same gain step on the reference path 350 and on thesignal path 301, and correct the error signal 334 if necessary so thatit corresponds to the physical gain error.

Another issue, which the controller 340 seeks to address, occurs whenthe detector dynamic range is smaller than the prescribed dynamic range.The APC loop must be deactivated for power levels that are outside theoperating range of the feedback path 360, which are mainly determined bythe power detector 322. In this case the system 300 works in open loopmode and the set value of the controller 340 becomes the wanted gain 341without any further modification even if an error signal 334 is present.

In closed loop mode, the set value delivered to the gain distributionunit 345 is a function of the wanted gain 341 and the error signal 334.Care must be taken in order to ensure a smooth transition when switchingbetween those two modes. Accordingly, another embodiment includes thecontroller 340 of FIG. 5 that limits the range of deviation from thewanted gain. In closed loop mode the gain range for the limitation isopened to its maximum value and in open loop mode the gain range of thelimitation is reduced to 0. Thus one embodiment of the controller 340 ofFIG. 5 fulfils both requirements (fast settling/smooth open-closed looptransition).

During operation of the controller 340 of FIG. 5, the error signal 334is delivered from the comparator block 332 and corresponds to thephysical gain error. A limiter 501 is necessary to guarantee a smoothtransition between the open loop mode and closed loop mode, as explainedabove. In the open loop mode, the limiter 501 is set to zero and forcesthe integrator 502 to operate with the wanted gain 341 as directed bylogic circuit 503. In closed loop mode the limiter 501 is used tocontrol the maximum deviation from the wanted gain 341. The gain 343 isthen applied on the distribution unit 345.

The gain distribution unit 345 is configured to appropriately set thegain of each block of the transmit chain (e.g., first, second and thirdsignal path PGAs 312 a-312 c and PA 316), so that the output power level(e.g., on transmission signal 318) is accurate. The input of this blockis only the set value from the controller 340. In one embodiment, thegain distribution unit 345 regulates one or more of the following: theamplitude of the digital amplitude information 308 at the input of DAC313, the amplitude of the baseband AM analogue signal 302 (with aprogrammable gain chain, or a combination of a DAC and a VGA), theamplitude of the RF signal after the signal path mixer 310 (with aprogrammable gain chain, or a combination of a DAC and a VGA), and thegain of the PA 316. In one embodiment of the power control system (e.g.,300), one or more of the proposed control or gain stages may be notimplemented.

Calibration of the power control systems of FIGS. 2 and 3 can be doneeasily. Only two constant envelope signals are necessary to calibratefor the two parameters (gain compensation and offset compensation)within the power control operation which is independent of themodulation scheme.

Thus, in accordance with the disclosure, one or more of the powercontrol systems (e.g., 200 of FIG. 2 or 300 of FIG. 3, respectively)described herein are operable to provide one or more or a combination ofthe following: a digital control loop using amplitude information fromor associated with the baseband, a comparator (e.g., 232 or 332) thatuses the ratio and not the just the difference of the reference signal(e.g., 205 or 305) and the measurement signal (e.g., 230 or 330), acontroller (e.g., 240 or 340) responsive to the gain on signal path(e.g., 203 or 301) as well as the gain on a reference path (e.g., 250 or350), a gain step response on the reference path (e.g., 250 or 350) andon the signal path (e.g., 203 or 301) plus feedback path (e.g., 260 or360) are matched.

The power control systems (e.g., 200 of FIG. 2 or 300 of FIG. 3,respectively) described herein are suitable for use in widebandcommunication systems including wireless or wireline technologies, forboth mobile and base station use, or where power control systems arerequired conforming to UMTS, CDMA, WCDMA, GSM, 3GSM and othercommunications standards, as well as in RF power control systemsrequiring output power control.

Although single filters are shown in FIGS. 2 and 3, filters 250, thepre-filter portion of ADC 228, digital filter 356 and 380, or analoguelow-pass filter 328 may individually comprise one or more filters.Similarly, although a single PGA of signal path amplifier 212 is shownin FIG. 2, signal path amplifier 212 may individually comprise one ormore amplifiers, switches, switched mode amplifier or another suitableRF switching circuit, for example, and as such are contemplated withinthe scope of the disclosure.

In addition to or in substitution of one or more of the illustratedcomponents, the illustrated PGAs, power amplifiers, controllers, gaindistribution unit, and other systems of the disclosure may includesuitable circuitry, state machines, firmware, software, logic, etc. toperform the various methods and functions illustrated and describedherein, including but not limited to the method(s) described below.

In one embodiment, a method is disclosed for closed loop power control(e.g., actuator signal 215 controlling the gain of PGA 212 of FIG. 2) ofan input signal (e.g., 202 of FIG. 2) such as a UMTS input signal basedon slow varying envelope information associated with the UMTS signal.

The method includes suppressing high frequencies (e.g., using referencepath filter 250 of FIG. 2) in an input signal (e.g., 202 of FIG. 2) togenerate a filtered envelope signal (e.g., 252 of FIG. 2), scaling(e.g., using reference path amplifier 254 of FIG. 2) the filteredenvelope signal 252 with a closed loop gain 204 to generate a referencesignal 205 therefrom, and amplifying (e.g., using PGA 212 of FIG. 2) anRF modulated signal 208 to generate an amplified signal path outputsignal 214 scaled by a gain of an actuator signal 215. The method alsoincludes detecting (e.g., using power detector 222 of FIG. 2) a power220 associated with the amplified and RF modulated signal 218 togenerate a detected power signal 224 therefrom, and converting (e.g.,using ADC 228 of FIG. 2) the detected power signal 224 into ameasurement signal 230. Finally, the method further includes generatingan error signal 234 (e.g., using comparator 232 of FIG. 2) based on adifference between the reference signal 205 and the measurement signal230, and generating the actuator signal (e.g., using controller 240 ofFIG. 2) for controlling the gain of the amplified signal path outputsignal 214 based on the error signal 234.

In another embodiment, the method further comprises comprising mixing toup-convert (e.g., using signal path mixer 210 of FIG. 2) the (e.g.,UMTS) input signal 302 with a local oscillator signal 206, beforeamplifying (e.g., using PGA 212 of FIG. 2) the RF modulated signal 202.

Although the disclosure has been illustrated and described with respectto one or more implementations, alterations and/or modifications may bemade to the illustrated examples without departing from the spirit andscope of the appended claims. In particular regard to the variousfunctions performed by the above described components or structures(assemblies, devices, circuits, systems, etc.), the terms (including areference to a “means”) used to describe such components are intended tocorrespond, unless otherwise indicated, to any component or structurewhich performs the specified function of the described component (e.g.,that is functionally equivalent), even though not structurallyequivalent to the disclosed structure which performs the function in theherein illustrated exemplary implementations of the disclosure. Inaddition, while a particular feature may have been disclosed withrespect to only one of several implementations, such feature may becombined with one or more other features of the other implementations asmay be desired and advantageous for any given or particular application.Furthermore, to the extent that the terms “including”, “includes”,“having”, “has”, “with”, or variants thereof are used in either thedetailed description and the claims, such terms are intended to beinclusive in a manner similar to the term “comprising”.

1. A closed loop power control system, comprising: a reference pathfilter coupled to an input signal, configured to suppress highfrequencies in the input signal and to generate a filtered envelopesignal; a reference path amplifier coupled to the reference path filterand a gain signal, configured to scale the filtered envelope signalbased on the gain signal and generate a reference signal therefrom; asignal path amplifier, configured to receive and amplify an RF modulatedsignal, and generate a signal path output signal scaled by a gain of anactuator signal; a power detector configured to detect a powerassociated with the scaled signal path output signal and to generate adetected envelope signal therefrom; an analog to digital converter (ADC)coupled to the power detector configured to receive, pre-filter andconvert the detected envelope signal into a measurement signal; acomparator block configured to receive the reference signal from thereference path amplifier and the measurement signal from the ADC, andgenerate an error signal based on the difference between the referencesignal and the measurement signal; and a controller coupled between thesignal path amplifier and the comparator block, configured to receivethe error signal from the comparator block and generate the actuatorsignal operable to control the gain of the signal path amplifier basedon the error signal.
 2. The power control system of claim 1, comprisinga power amplifier coupled to the signal path amplifier, configured toamplify the power of the scaled signal path output signal and generatean RF transmission signal.
 3. The power control system of claim 2,comprising an antenna coupled to the power amplifier, configured totransmit the RF transmission signal.
 4. The power control system ofclaim 2, wherein the power amplifier comprises two or more switched modepower amplifiers.
 5. The power control system of claim 1, comprising asignal path mixer configured to up-convert the input signal at thereference path filter with a local oscillator signal, and to supply theRF modulated signal result therefrom to the signal path amplifier. 6.The power control system of claim 1, wherein the input signal ismodulated according to one of a UMTS, CDMA, WDCMA, GSM and 3GSMstandard.
 7. The power control system of claim 1, wherein the controlleris configured to integrate and low-pass filter the error signal in thegeneration of the actuator signal.
 8. The power control system of claim1, wherein the controller is configured to integrate the error signal inthe generation of the actuator signal.
 9. The power control system ofclaim 1, wherein the analog to digital converter comprises a low-passpre-filter.
 10. The power control system of claim 1, wherein the controlsystem is configured to scale the UMTS input signal by the actuatorsignal based on a mismatch between the reference signal generated on areference signal path and the measurement signal generated on a feedbackpath.
 11. A closed-loop power control system, comprising: a referencepath comprising a delay adjustment block coupled to a baseband inputsignal, configured to adjustably delay the baseband input signal; areference path programmable gain amplifier (PGA), configured to receiveand amplify the delayed baseband input signal, and generate a referencepath PGA output signal scaled by a gain associated with a controllersignal; and a digital filter coupled to the scaled reference PGA outputsignal, configured to suppress high frequencies in the scaled referencepath PGA output signal and to generate a reference signal; a signal pathcomprising first, second and third signal path PGAs, configured toreceive and amplify one of the baseband input signal and an RF modulatedsignal, scaled by respective first, second and third gain signals, thethird signal path PGA further configured to provide a scaled PGA outputsignal at an output of the third signal path PGA; a digital to analogconverter (DAC) coupled between the first and second signal path PGAs,configured to convert the digital components of the amplified basebandinput signal from the first signal path PGA to an analog baseband inputsignal which is amplified by the second signal path PGA; and a signalpath mixer coupled between the second and third signal path PGAs,configured to up-convert the amplified analog baseband input signal fromthe second signal path PGA with a local oscillator signal (complexcarrier signal), and to supply an RF modulated signal result therefromto the third signal path PGA; a feedback path comprising a powerdetector coupled to the third signal path PGA, configured to detect apower associated with the scaled PGA output signal and to generate adetected envelope signal therefrom; an analog to digital converter (ADC)coupled to the power detector configured to receive, pre-filter andconvert the detected envelope signal into a filtered digital measurementsignal; and a digital filter coupled to the analog to digital converter,configured to suppress high frequencies in the digital measurementsignal and to generate a measurement signal; a control circuitcomprising a comparator block configured to receive the reference signalfrom the reference path and the measurement signal from the feedbackpath, and generate an error signal based on the difference between thereference signal and the measurement signal; a controller coupledbetween a gain distribution unit and the comparator block configured toreceive the error signal from the comparator block and a wanted gaininput signal and generate the control signal operable to control thegain of the gain distribution unit and the controller signal operable tocontrol the gain of the reference path PGA based on the error signal;and the gain distribution unit coupled between the controller and thefirst, second and third signal path PGAs, configured to receive thecontrol signal from the controller and generate the actuator signaloperable to control the gain of the first, second and third signal pathPGAs based on the error signal.
 12. The power control system of claim11, comprising a power amplifier coupled to the output of the thirdsignal path PGA, configured to amplify the power of the scaled PGAoutput signal.
 13. The power control system of claim 11, wherein thefeedback path further comprises a gain compensation circuit and anoffset compensation circuit, configured to generate a gain and offsetcompensation for the digital measurement signal.
 14. The power controlsystem of claim 11, comprising an antenna coupled to the output of thethird signal path PGA, configured to transmit the scaled PGA outputsignal.
 15. The power control system of claim 11, wherein the inputsignal is modulated according to one of a UMTS, CDMA, WDCMA, GSM and3GSM standard.
 16. The power control system of claim 11, wherein thefeedback path further comprises an analogue offset compensation circuit,configured to generate analogue offset compensation for the filtereddigital measurement signal.
 17. A power control system, comprising:reference path filtering means operable to suppress high frequencies ina baseband input signal and to generate a filtered baseband signal;amplifying means operable to scale the filtered baseband signal based ona closed loop gain and generate a reference signal therefrom; amplifyingmeans operable to amplify an RF modulated signal and generate anamplified output signal scaled by a gain of an actuator signal; powerdetecting means operable to detect a power associated with the amplifiedand RF modulated signal and generate a detected envelope signaltherefrom; converting means operable to receive, pre-filter and convertthe detected envelope signal into a measurement signal; comparing meansoperable to generate an error signal based on a difference between thereference signal and the measurement signal; and controlling meansoperable to receive the error signal and generate the actuator signaloperable to control the gain of the amplifying means based on the errorsignal.
 18. The power control system of claim 17, comprising poweramplifying means operable to amplify the power of the amplified outputsignal to generate a transmission signal.
 19. The power control systemof claim 18, comprising a transmitting means operable to transmit thetransmission signal generated by the power amplifying means.
 20. Thepower control system of claim 17, comprising a mixing means operable toup-convert the baseband input signal with a local oscillator signal, andto supply the RF modulated signal result to the amplifying means.
 21. Amethod for closed loop power control of an input signal based on slowvarying envelope information associated with the input signal, themethod comprising: suppressing high frequencies in a input signal togenerate a filtered envelope signal; amplifying the filtered envelopesignal with a closed loop gain to generate a reference signal therefrom;amplifying an RF modulated signal to generate an amplified output signalscaled by a gain of an actuator signal; detecting a power associatedwith the amplified and RF modulated signal to generate a detectedenvelope signal therefrom; converting the detected envelope signal intoa measurement signal; generating an error signal based on a differencebetween the reference signal and the measurement signal; and generatingthe actuator signal for controlling the gain of the amplified outputsignal based on the error signal.
 22. The method of claim 21, comprisingmixing to up-convert a UMTS input signal with a local oscillator signal,before amplifying the RF modulated envelope signal.